This invention relates to a magnetic recording medium.
At the present time, the magnetic recording medium commonly consists of a backing material coated with a mixture of magnetic powder and binder. With the expanding applications, there is a growing demand for further improvements in properties of the medium.
The binders thus far employed widely have been two-component combinations of vinyl chloride-vinyl acetate, acrylonitrile, cellulose, urethane, ester, ethylene, epoxy and other resins, especially the combinations of a polyurethane resin with a vinyl chloride-vinyl acetate copolymer resin or with a nitrocellulose resin. Those two-component binders have, however, had a disadvantage in that the electromagnetic conversion and physical properties of the resulting magnetic coating are antagonistic in relation to the mixing ratio of the two binder components and therefore it is extremely difficult to meet the both property requirements, and attainment of satisfactory properties cannot be expected.
In view of these, the present invention has for its object the provision of a magnetic recording medium improved in the electromagnetic conversion characteristic that is most important and indispensable of the requirements for a medium of this character and in repeated running stability and bonding strength, both typical of the physical properties required, without impairing the usually antagonistic property of surface smoothness.
It has now been found that a magnetic recording medium generally superior to the conventional medium containing the two-component binder in properties, such as the stability on repeated runs past the head, bonding strength, electromagnetic conversion characteristic, and gloss, can be manufactured by employing a three-component system of a polyurethane resin, a phenoxy resin, and a vinyl chloride-vinylidene chloride resin as the binder of the magnetic coating material for the medium.